Automatic choke



Dec. 2, 1958 e. NASTAS AUTOMATIC CHOKE Filed June 12, 1957 George Nastas, Livonia,

AUTOMATIC CHOKE Mich., assignor to Ford Motor Company, Dearborn, Miclin, a corporation of Delaware Application June 12, 1957, Serial No. 665,287 5 Claims. (Cl. 123- 119) This invention relates to the art of internal combustion engine carburetion and more specifically to a particular improvement in an automatic choke for the regulation of internal combustion engine carburetors.

The increasing use of automatic chokes on vehicular internal combustion engines to relieve the operator of the necessity of manually choking the carburetor during cold weather operation has brought to light several shortcomings in these devices as commercially marketed. One of the most annoying difficulties with automatic chokes has been the inability of the thermal element which operates the automatic choke to faithfully mirror the thermal conditions within the induction system of the engine. This is particularly manifest where a thoroughly warmed engine is stopped briefly and then an attempt is made to restart the engine. Under these circumstances the thermal element in automatic chokes new in use will cool much more rapidly than the massive engine and, hence, will establish a choked condition upon a thoroughly warmed engine with the concomitant starting difficulties and waste of fuel.

The instant invention has been developed specifically to alleviate this deficiency and has been explained in conpunction with the figures of drawing in which,

Figure l is a showing, in a somewhat schematic fashion, of the essential. elements of one form of an automatic choke, and,

Figure 2 is a sectional view of a portion of Figure 1.

It is conventional practice in automotive carburetion design to employ a stream of heated air to cause the operation of an automatic choke. This stream of heated air is usually derived from the main air induction system down stream from the air cleaner and is drawn by manifold suction through a refractory metal tube directly exposed to exhaust gas wherein it is heated. This heated air is drawn over the operating mechanism of the automatic choke and then discharged into the intake manifold.

In the conventional automatic choke, the bimetal element which actuates the choking mechanism is arranged to be heated either by direct contact with the stream of hot air from the refractory metal tube, or indirectly by heat obtained from this heated stream of air by conduction through a control plate. When a cold engine is first started, the heating of the bimetal element is accomplished by direct contact with the stream of hot air. As the engine warms up, the direct contact of the heated air stream and the bimetal element is interrupted and further and slower heating of the bimetal element is accomplished by heat which is conducted through a metal control plate.

The present invention operates in a similar manner with one'vital exception. The initial heating of the bimetal is accomplished by direct contact with a stream of heated air and later heating by heat conducted through a control plate. However, after the engine has been heated to normal operating temperature and the choke element 18 is possible.

valve has been completely or almost completely opened, the bimetal element and its surroundings are again subjected to direct contact with a stream of heated air and heated to a temperature far in excess of that which could be obtained only by heat being conducted through a control plate. When the bimetal and its surroundings have been heated to this extent they serve as a high head heat reservoir and prevent the premature application of the choke during the time required for the heated engine to cool to the point where choking is necessary for proper starting.

Referring to Figures 1 and 2, the heated stream of air is introduced into conduit 10 from the refractory metal heating tube. The heated air flows through conduit 10 and is discharged through opening 11 just under control plate 12. The hot gas stream exits through opening 13 and conduit 14.

Control plate 12 is rotatably mounted on pivot 15 which is rigidly secured to base 16. Figure l clearly shows control plate 12 to be provided with four openings. 17. A study of Figure 2 will show that the heated air stream in passing from conduit 10 to conduit 14 may either flow through space 24 between control plate 12 and base 16, or it may flow through opening 11, matching opening 17, across bimetal element 18 and out through another opening 17 and match ing opening 13. The stream of heated gas is confined to the first mentioned path when the openings in the control plate 12 do not coincide with the corresponding openings in base 16. At such times the only heat which can reach bimetal element 18 must pass through control plate 12 by conduction. When the two sets of openings do coincide, the bimetal element 18 is rapidly heated by being in direct contact with the heated stream of Figure 1 shows the control plate 12 in the position assumed with the bimetal element 18 completely chilled and the choke valve fully closed. In this position one of the two pairs of openings 17 are aligned with openings 11 and 13 and a direct flow of heated air across bimetal As the engine warms, the motion of "bimetal element 18 rotates control plate 12 in "a clockwise direction and interrupts the alignment between openings 17 and openings 11 and 13. Heat is then slowly conducted through control plate 12 resulting in a slow continued opening of the choke valve.

Further soaking of heat through control plate 12 to bimetal element 18 causes further rotation of control plate 12 in a clockwise direction until the other pair of openings 17 are aligned with openings 11 and 13 in stationary base 16. This again permits the rapid application of heat to bimetal element 18 and its container. This high rate of heat application results in bimetal element 18 and its container becoming stabilized as to temperature at a much higher value than would be possible by the simple conduction of heat through control element 12. The rotation of control plate 12 is mechanically stopped to prevent this high temperature from carrying the control plate 12 clockwise past the point of coincidence of the openings 11 and 13 and the second pair of openings 17 in the control plate 12.

As in conventional automatic chokes, the motion of bimetal element 18 is transmitted through a rotatable arm 19, shaft 21 and lever 20 and an appropriate linkage system to a choke valve 22. Choke valve 22 is in turn provided with a pressure sensitive, spring biased valve 23 which prevents the generation of an excessive vacuum in the intake manifold due to operation of the automatic choke. I

I claim as my invention:

1. An automatic choke for an internal combustion engine comprising a temperature sensitive element for troli-rneans for shunting-the heated stream'of gas-out of direct contact with the temperature sensitive element;

said control meanspermitting-direct contact of the'heatedgas 5 stream upon the temperature a sensitive elementwhen the temperature'sensitive element is below a fixed lower temperature and also Whenthe temperature sensitive elem'entisabove-a fixed upper temperature and shuntingthe -hot'-streamof-=gas out ofdirect contact with the temperature sensitive element when the temperature sensitive element is at any temperatureintermediatesaid upper and lower temperatures.

23-An automatic choke foran internal combustion engine comprising a temperature sensitive element for actuating" thechoking means, means for applying heat generated by-engine operation to the temperature sensitive element, and control means for regulating the application' of suchheat to the temperature sensitive element; said control means permitting the rapid application of heat to the temperature sensitiveelement when thetemperature sensitive element is below a fixed lower temperature and'permittinga similar rapid application of heat to thetemperature sensitive element when the temperature sensitive element is above a fixed upper temperature; and permitting aless rapid application of heat-'tothe temperature sensitive element when the tem-.

peratu're ofthe temperature sensitive element is intermediate said' lower fixed temperature and said upper fixed temperature.

3; Anautomatic choke for an internal combustion engine comprising a temperature sensitive element for actuating" thechoking means, means for delivering a heated stream of gas adjacent the temperature'sensitlve means, means for removing the heated stream of gas from adjacent theternperature sensitive means and control means operated by the-temperature sensitive means for shunting the heatedstream of gas out of direct con ta'ctwith thete'mperature sensitive element, said control means permitting'direct contact'of the heated gas stream upon the temperature sensitive element when the temperature sensitive" element is below a fixed lower temperature and-also when the temperature sensitive element is above a fixed upper temperature andshunting the hot stream of gas out of direct contact with the temperature sensitive element when the temperature sensitive element is at any temperature intermediate said upper and lower temperatures.

4. An automatic choke'for an internal combustion 7 engine comprising a temperature sensitive element for actuating the choking means, meansfor applying heat generated by engine operation to the temperature sensitive element, and control means operated by the temperature sensitive means for regulating the application of such heat to the temperature sensitive element, said control means pennittingthe rapid applicationof heat to the temperature sensitiveelement when the temperature sensitive element is below a fixed lower temperature and permitting a similar rapid application of heat to the temperature sensitive element when the temperature-sensitive element is above a fixed upper temperature, and permitting a-less rapid application of heattothe-temperature sensitive-elementwhen the temperature of'the temperature-sensitive element-is intermediate 'said lower fixed" temperature and said 'upperfixedtemperature.

5. An automatic choke for an internal combustionengine comprising a temperature'sensitive element for actuating the choking means; an opening-for discharg ing heated gas adjacent the temperature sensitive element, a second opening for-removing heated'gas'adja cent the'temperature sensitive element, and a control plate-operated by the temperature sensitive element and plate, one of said ports being adjacent the opening for the discharge of hot gas and other port of said pair being opposite the opening for the removal of hot gas when the temperature of the temperaturesensitive'element is'below a fixed lowertemperature, and a second pair of ports through the control plate; one of said" second pair of ports being adjacent the opening for'the discharge of'hot gas and the other port of said second pair being opposite'theopening forthe removal of hot' gaswhen the-temperature'of' the temperature sensitive element is above a fixed upper temperature.

No references cited. 

